D.N. Angel is based on a manga series written and illustrated by Yukiru Sugisaki.

Daisuke Niwa is a 14-year-old boy with a secret. He has a special genetic ability: when he sees or thinks about Risa Harada, a girl he has a crush on, he turns into an infamous thief named Dark. However, after Risa rejects Daisuke's feelings, he develops a crush on Risa's twin sister, Riku Harada. Unlike her sister, Riku returns Daisuke's feelings. Risa, meanwhile, develops a crush on Dark, not knowing that Dark and Daisuke are the same person. When he's not Dark, Daisuke is skilled in dodging traps, picking locks, and other thieving skills.

Dark steals cursed art pieces made by the Hikari family and seals them away to prevent the pieces from causing any more trouble. Dark appears in the first male in each generation of the Niwa family. At the start of the series, Dark had been dormant for 40 years, because his last host (Daisuke's grandfather) only had one female offspring (Daisuke's mother). Daisuke's mother was very determined to have a son, so Dark could return. When she married Daisuke's father, he took on the Niwa last name, so the name could continue into future generations. The Niwa family has a fluffy white pet named Wiz, which is also Dark's familiar. Wiz has the ability to transform into both Daisuke and Dark.

Satoshi Hiwatari is in the same school as Daisuke and the Harada twins, and he is the last heir of the Hikari family. Satoshi is actually the commander in charge of the police force investigating Dark, and he also has an alter ego named Krad (who is Dark's worst enemy). Satoshi is calm and composed, and rarely shows his feelings. This causes many people to think he's distant and cold.

While D.N. Angel doesn't have any visual content that would be inappropriate for younger viewers, I think some of the concepts presented in the series would be harder for younger viewers to understand. Personally, I would recommend the series to anime viewers who are 13 or 14 years of age and older.